Differential recurrent laryngeal nerve palsy rates after thyroidectomy

Avoiding Complications of Thyroidectomy: Recurrent Laryngeal Nerve and Superior Laryngeal Nerve Preservation

Both the superior and recurrent laryngeal nerves are at risk for injury during thyroid surgery. Comprehensive preoperative evaluation is key for surgical planning. Exposing nerves through careful dissection is the safest strategy to minimize injury risk. Intraoperative neural monitoring can be beneficial for both identifying and preserving the nerves.

Changes in vocal fold gene expression and histology after injection augmentation in a recurrent laryngeal nerve injury model

OBJECTIVE

To investigate changes in neuroregenerative pathways with vocal fold denervation in response to vocal fold augmentation.

METHODS

Eighteen Yorkshire crossbreed swine underwent left recurrent laryngeal nerve transection, followed by observation or augmentation with carboxymethylcellulose or calcium hydroxyapatite at two weeks. Polymerase chain reaction expression of genes regulating muscle growth (MyoD1, MyoG and FoxO1) and atrophy (FBXO32) were analysed at 4 and 12 weeks post-injection. Thyroarytenoid neuromuscular junction density was quantified using immunohistochemistry.

RESULTS

Denervated vocal folds demonstrated reduced expression of MyoD1, MyoG, FoxO1 and FBXO32, but overexpression after augmentation. Healthy vocal folds showed increased early and late MyoD1, MyoG, FoxO1 and FBXO32 expression in all animals. Neuromuscular junction density had a slower decline in augmented compared to untreated denervated vocal folds, and was significantly reduced in healthy vocal folds contralateral to augmentation.

CONCLUSION

Injection augmentation may slow neuromuscular degeneration pathways in denervated vocal folds and reduce compensatory remodelling in contralateral healthy vocal folds.

Retrospective Cohort Study on the Surgical Outcomes of Intracapsular Thyroidectomy Vs Standard Thyroidectomy

The focal point of thyroidectomy surgery has always been to reduce the incidence of inadvertent damage to the recurrent laryngeal nerve(RLN). The intracapsular thyroidectomy is one such technique with minimum chance of injuring the nerve. To compare retrospectively the surgical outcomes between the two methods of thyroidectomy-coventional thyroidectomy Vs intracapsular thyroidectomy. Materials and methods-55 cases of benign thyroid disease for whom thyroidectomy was performed in our hospital between the period of 2019-2022 were compared retrospectively. Out of these 34 cases had undergone intracapsular thyroidectomy and 21 cases underwent routine extracapsular thyroidectomy. The surgical outcomes including operation time, pain, postoperative infection, postoperative hypocalcemia, postoperative recurrent laryngeal nerve paralysis and mean hospital stay were analyzed. The mean operating time were very low in the intracapsular limb as compared to the other group. The pain and the mean hospital stay was also far lesser for the intracapsular limb. Both cohorts had no incidence of hypocalcemia. The incidence of recurrent laryngeal nerve palsy was very low in the intracapsular cohort (only 1 case of temporary unilateral RLN palsy), whereas it was higher in the routine extracapsular cohort (5 cases of permanent palsy). The risk of having vocal cord palsy (left/right) is 1.172 times more with conventional/standard thyroidectomy as compared to intracapsular thyroidectomy. Intracapsular technique is a much more rewarding method to perform thyroidectomy, without the risk of the recurrent laryngeal nerve palsy as compared to routine thyroidectomy.

A Prospective Study of Electromyographic Amplitude Changes During Intraoperative Neural Monitoring for Open Thyroidectomy

BACKGROUND

Intraoperative nerve monitoring (IONM) of the vagus and recurrent laryngeal nerve (RLN) enables prediction of postoperative nerve function. The underlying mechanism for loss of signal (LOS) in a visually intact nerve is poorly understood. The correlation of intraoperative electromyographic amplitude changes (EMG) with surgical manoeuvres could help identify mechanisms of LOS during conventional thyroidectomy.

METHODS

A prospective study of consecutive patients undergoing thyroidectomy was performed with intermittent IONM using the NIM Vital nerve monitoring system. The ipsilateral vagus and RLN was stimulated, and vagus nerve signal amplitude recorded at five time points during thyroidectomy (baseline, after mobilisation of superior pole, medialisation of the thyroid lobe, before release at Ligament of Berry, end of case). RLN signal amplitude was recorded at two time points; after medialisation of the thyroid lobe (R1), and end of case (R2).

RESULTS

A total of 100 consecutive patients undergoing thyroidectomy were studied with 126 RLN at risk. The overall rate of LOS was 4.0%. Cases without LOS demonstrated a highly significant vagus nerve median percentage amplitude drop at medialisation of the thyroid lobe (- 17.9 ± 53.1%, P < 0.001), and end of case (- 16.0 ± 47.2%, P < 0.001) compared to baseline. RLN had no significant amplitude drop at R2 compared to R1 (P = 0.207).

CONCLUSIONS

A significant reduction in vagus nerve EMG amplitude at medialisation of the thyroid and the end of case compared to baseline indicates that stretch injury or traction forces during thyroid mobilisation are the most likely mechanism of RLN impairment during conventional thyroidectomy.

The Causes and Laryngeal Electromyography Characteristics of Unilateral Vocal Fold Paralysis

OBJECTIVE

To investigate the causes and laryngeal electromyography (LEMG) characteristics of unilateral vocal fold paralysis (UVFP).

METHODS

We retrospectively analyzed the history and LEMG of 337 patients with unilateral vocal fold immobility. The etiology was reviewed and the characteristics of LEMG (including spontaneous potential, recruitment potential, evoked potential, synkinesia, and et al.) were analyzed.

RESULTS

The causes included injury (177 cases, 52.5%), idiopathic causes (72 cases, 21.4%), infection (61 cases, 18.1%), tumor and compressive factors (27 cases, 8.0%). Among the injury group, 161 cases were caused by surgery (111 cases of thyroid surgery), and 16 cases were caused by trauma. LEMG showed that complete nerve injury was present in 72.9% of the injury group, 66.7% of the tumors or compressive factors group, 49.2% of the infection group, and 44.4% of the idiopathic group. Of the 337 patients, 136 patients (40.4%) had synkinesia in the posterior cricoarytenoid muscles, and only two of these patients also had synkinesia in the thyroarytenoid muscles. The proportion of complete recurrent laryngeal nerve (RLN) injury in patients with synkinesia was higher than that of patients without synkinesia.

CONCLUSION

The main cause of vocal fold paralysis is neck surgery, most commonly thyroid surgery. Patients with different causes of paralysis had different severities of RLN injury. LEMG showed that surgery or trauma accounted for the highest proportion of complete nerve injury. Patients with severe RLN injury were more prone to synkinesia, and the posterior cricoarytenoid muscles were more likely to have synkinesia than the thyroarytenoid muscles.

An Audit of the Procedure of Open Thyroidectomy at A Tertiary Care Centre

We plan to evaluate the various variables associated with the complications of thyroidectomy performed at our department in the last 5 years. Medical records of the patients who underwent thyroidectomy during 2014-2018 were collected. Complications of hypocalcemia and recurrent laryngeal nerve palsy were analysed in terms of the demography, cytopathology and the extent of surgery. Student's t-test, Mann-Whitney U-test, Fisher exact test and chi square test were applied to look for any significant associations. P value < 0.05 was considered significant. 123 patients were analysed (87 females, 38 males). Mean age was 38.3 years (range 11-71 years). Most common cytopathology was papillary carcinoma thyroid (Bethesda VI) - 43/123 (35%). 107 of these 123 patients underwent primary surgery, 10 underwent revision surgery while 6 underwent completion thyroidectomy. Seven patients incurred RLN palsy out of which 3 were temporary. RLN palsy was seen in only malignant cases (p < 0.05). Incidence was higher in T4a stage (p < 0.05). However, it had no association with a simultaneous central or lateral neck dissection. Hypocalcemia was seen in 22 patients (17.8%), out of whom 9 patients developed permanent hypocalcemia. It was seen significantly higher in patients undergoing central neck dissection (p < 0.05) and in malignant thyroid lesions (p < 0.05). Gender, age and the cytopathology had no bearing on RLN palsy and hypoparathyroidism. Malignant thyroid lesions had a significantly higher incidence of RLN palsy and hypoparathyroidism. A thorough anatomical knowledge can reduce the incidence of these complications.

Augmentation and vocal fold biomechanics in a recurrent laryngeal nerve injury model

Objectives/hypothesis

Composite vocal fold (VF) biomechanical data are lacking for augmentation after recurrent laryngeal nerve (RLN) injury. We hypothesize resulting atrophy decreases VF stiffness and augmentation restores native VF biomechanics.

Methods

Sixteen Yorkshire Crossbreed swine underwent left RLN transection and were observed or underwent carboxymethylcellulose (CMC) or calcium hydroxyapatite (CaHa) augmentation at 2 weeks. Biomechanical measurements (structural stiffness, displacement, and maximum load) were measured at 4 or 12 weeks. Thyroarytenoid (TA) muscle cross‐sectional area was quantified and compared with two‐way ANOVA with Tukey's post hoc test.

Results

After 4 weeks, right greater than left structural stiffness (mean ± SE) was observed (49.6 ± 0.003 vs. 28.4 ± 0.002 mN/mm), left greater than right displacement at 6.3 mN (0.54 ± 0.01 vs. 0.46 ± 0.01 mm, p < .01) was identified, and right greater than left maximum load (72.3 ± 0.005 vs. 40.8 ± 0.003 mN) was recorded. TA muscle atrophy in the injured group without augmentations was significant compared to the noninjured side, and muscle atrophy was seen at overall muscle area and individual muscle bundles. CMC augmentation appears to maintain TA muscle structure in the first 4 weeks with atrophy present at 12 weeks.

Conclusions

VF biomechanical properties match TA muscle atrophy in this model, and both CMC and CaHa injection demonstrated improved biomechanical properties and slower TA atrophy compared to the uninjured side. Taken together, these data provide a quantifiable biomechanical basis for early injection laryngoplasty to improve dysphonia and potentially improve healing in reversible unilateral vocal fold atrophy.

Level of evidence

N/A

Preoperative serum calcitonin may improve initial surgery for medullary thyroid cancer in patients with indeterminate cytology

BACKGROUND

Medullary thyroid cancer (MTC) is rare, with poorer outcomes than differentiated thyroid cancer. We aimed to identify areas for improvement in the pre-operative evaluation of patients with possible MTC in a high-volume endocrine surgery unit in accordance with current practice guidelines. We hypothesised that the selective use of serum calcitonin (sCT) as a biomarker for possible MTC could guide the extent of initial surgical management.

METHODS

We recruited MTC patients between 2000 and 2020 from the Monash University Endocrine Surgery Unit database. Demographics, tumour characteristics, pre-operative evaluation, operative management, and outcomes were analysed.

RESULTS

Of 1454 thyroid cancer patients, 43 (3%) had MTC. Pre-operatively, 36 (84%) patients with MTC confirmed on cytology (28, 65%), elevated sCT (6, 14%) or RET mutation (2, 4%). Of these 36 patients, 31 (86%) had optimal extent of thyroidectomy and lymph node dissection (LND). Five (14%) had less than total thyroidectomy due to nerve injury. Thirty-four patients had compartmental LND. In the 12 (27%) patients with indeterminate or non-diagnostic cytology, 5 had elevated sCT and were managed as above. None of the remaining seven had LND, thus potentially suboptimal surgery.

CONCLUSION

Our findings reflect the rarity of MTC, and the challenges of pre-operative diagnosis. The addition of sCT may improve surgical planning in patients with indeterminate cytology.

Recurrent Laryngeal Nerve Paralysis Following Thyroidectomy: Analysis of Factors Affecting Nerve Recovery

OBJECTIVES

Paralysis of the recurrent laryngeal nerves (RLNs), albeit decreased over the years, leaves the surgeon helpless as there is not much that can be done once it occurs. Nimodipine has been suggested as a remedy that could accelerate the recovery of the nerve. Our study aimed to examine the factors that affect the recovery rate (RR) and time to recovery (TTR) of post-thyroidectomy RLN paralysis, with an emphasis on the use of nimodipine.

METHODS

A total of 197 patients who had undergone thyroid and parathyroid surgeries were retrospectively reviewed from October 2016 to August 2019. Patients who had RLN paralysis following surgery were assessed. The medical records were retrospectively analyzed to look for possible factors that may influence RLN recovery.

RESULTS

A total of 289 nerves were at risk. Temporary RLN paralysis rate was 7.9% while 1.7% was permanent. Age (odds ratio [OR] = 4.8) and intra-operative extra-thyroid extension (OR = 9.0) were independent risk factors for RLN paralysis. The rate of recovery was 82.1%. Loss of signal (LOS; P = .066) was a factor trending for an impact on RR but not nimodipine (P > .05). The mean TTR was 32 days. LOS, nimodipine, and steroid use, among others, were factors trending for an impact on the TTR.

CONCLUSION

Although not reaching statistical significance, nimodipine and steroids might influence TTR but not the RR. Larger studies are warranted to address the effect of nimodipine on the outcome of RLN paralysis.

LEVEL OF EVIDENCE

4 Laryngoscope, 2022.

Varied Recurrent Laryngeal Nerve Course Is Associated with Increased Risk of Nerve Dysfunction During Thyroidectomy: Results of the Surgical Anatomy of the Recurrent Laryngeal Nerve in Thyroid Surgery Study, an International Multicenter Prospective Anatomic and Electrophysiologic Study of 1000 Monitored Nerves at Risk from the International Neural Monitoring Study Group

Background: The recurrent laryngeal nerve (RLN) can be injured during thyroid surgery, which can negatively affect a patient's quality of life. The impact of intraoperative anatomic variations of the RLN on nerve injury remains unclear. Objectives of this study were to (1) better understand the detailed surgical anatomic variability of the RLN with a worldwide perspective; (2) establish potential correlates between intraoperative RLN anatomy and electrophysiologic responses; and (3) use the information to minimize complications and assure accurate and safe intraoperative neuromonitoring (IONM). Methods: A large international registry database study with prospectively collected data was conducted through the International Neural Monitoring Study Group (INMSG) evaluating 1000 RLNs at risk during thyroid surgery using a specially designed online data repository. Monitored thyroid surgeries following standardized IONM guidelines were included. Cases with bulky lymphadenopathy, IONM failure, and failed RLN visualization were excluded. Systematic evaluation of the surgical anatomy of the RLN was performed using the International RLN Anatomic Classification System. In cases of loss of signal (LOS), the mechanism of neural injury was identified, and functional evaluation of the vocal cord was performed. Results: A total of 1000 nerves at risk (NARs) were evaluated from 574 patients undergoing thyroid surgery at 17 centers from 12 countries and 5 continents. A higher than expected percentage of nerves followed an abnormal intraoperative trajectory (23%). LOS was identified in 3.5% of NARs, with 34% of LOS nerves following an abnormal intraoperative trajectory. LOS was more likely in cases of abnormal nerve trajectory, fixed splayed or entrapped nerves (including at the ligament of Berry), extensive neural dissection, cases of cancer invasion, or when lateral lymph node dissection was needed. Traction injury was found to be the most common form of RLN injury and to be less recoverable than previous reports. Conclusions: Multicenter international studies enrolling diverse patient populations can help reshape our understanding of surgical anatomy during thyroid surgery. There can be significant variability in the anatomic and intraoperative characteristics of the RLN, which can impact the risk of neural injury.

Selecting the Right Plane of Dissection in Thyroidectomy: Along the Recurrent Laryngeal Nerve or the Thyroid Capsule? A Retrospective Analysis

Introduction  Total thyroidectomy remains highly technical, with a significant risk of recurrent laryngeal nerve (RLN) compromise and hypoparathyroidism. After identifying RLN, at the level of the ligament of Berry, local factors may compel the surgeon to either dissect along the nerve or the thyroid capsule.

Objective  The objective of the present study is to compare these two approaches in terms of outcomes and complication rates.

Methods  This is a retrospective analysis from September, 2013 to April 2019 of 511 consecutive patients undergoing thyroidectomy. General demographics and disease parameters were recorded. At the discretion of the surgeon and according to the demands of the local operative factors, the patients either had dissection along the RLN or along the thyroid capsule. Perioperative and postoperative parameters such as blood loss, duration of surgery, hospital stay, pain scores, analgesia requirements and complications were recorded. The groups were compared with the Pearson chi-squared test or with the Fisher exact test. A p-value < 0.05 was considered statistically significant.

Results  The incidence of transient hypocalcaemia and transient RLN compromise were higher when dissection was performed along the nerve as opposed to the plane along the thyroid capsule. Other parameters including operative time, hospital stay, pain scores, analgesia requirement, wound infection, seroma, hemorrhage, and recurrence did not differ between the groups. Subgroup analysis of the patients who presented with complications showed that local factors, malignancy, and extent of surgery correlated positively with complications when dissected along the RLN.

Conclusion  Dissection along the capsule of the thyroid during thyroidectomy is a safer plane in terms of low rate of transient RLN injury and hypoparathyroidism as opposed to dissection along the nerve.

The circumstances in which recurrent laryngeal nerve palsy occurs after surgery for benign thyroid disease: a retrospective study of 1026 patients

OBJECTIVE

To evaluate the circumstances in which recurrent laryngeal nerve palsy occurs after thyroid surgery.

METHODS

This study assessed 1026 patients who underwent surgery for benign thyroid disease over a seven-year period in a retrospective, single-centre study.

RESULTS

With a total of 1835 recurrent laryngeal nerves at risk, there were 38 cases (2.07 per cent) of transient recurrent laryngeal nerve palsy and 8 (0.44 per cent) of permanent recurrent laryngeal nerve palsy. No explanation was found for 10 of the 46 cases of recurrent laryngeal nerve palsy. Among the 38 other cases, the probable causes included poor identification of the recurrent laryngeal nerve during surgery, involuntary resection of the nerve and several other factors.

CONCLUSION

Apart from accidental resection of the recurrent laryngeal nerve during thyroid surgery, the causes of post-operative recurrent laryngeal nerve palsy are often unclear and likely multifactorial. Poor identification of the recurrent laryngeal nerve during surgery is still the main cause of post-operative recurrent laryngeal nerve palsy, even when intra-operative neuromonitoring is used.

Experience with the use of intraoperative continuous nerve monitoring in video-assisted neck surgery and external cervical incisions

OBJECTIVES

Recurrent laryngeal nerve (RLN) injury is one of the severe complications in thyroid surgery. Therefore, intraoperative nerve monitoring (IONM) has been widely used to identify the RLN and confirm its integrity. Recently, the usefulness of continuous IONM (CIONM) with automatic, periodic stimulation to the vagus nerve during thyroid surgery was reported. This study aimed to report our experience with minimally invasive video-assisted endoscopic endocrine neck surgery (VANS), during which, CIONM was successfully applied for the first time.

METHODS

Consecutive patients who underwent thyroid surgery with CIONM, performed in our department using either external neck incision surgery or VANS between July 2017 and June 2019, were retrospectively analyzed.

RESULTS

A total of 22 patients who underwent thyroid surgery with neck incision (14 cases; 7 men and 7 women; age, 21-75 years [mean, 52 years]) or VANS (8 cases; 8 women, age, 20-61 years [mean, 41 years]) were enrolled in this study. The addition of CIONM in VANS prolonged the operation's duration by approximately 30 minutes as the endoscopic surgery was technically more difficult. No intra- and postoperative incidence of transient or permanent RLN palsy was observed in any patient, except for three patients who underwent external neck incision surgery in whom combined resection was unavoidable due to tumor invasion of the RLN.

CONCLUSION

We reported the first successful application of CIONM during thyroidectomy using VANS. Future clinical trials should clarify the benefits of CIONM when compared to intermittent IONM in VANS.

LEVEL OF EVIDENCE

5.

Association Between Recurrent Laryngeal Nerve Calibre and Body Figure: A Preoperative Tool to Assess Thin-Diameter Nerves in Thyroidectomy

Inadvertent recurrent laryngeal nerve (RLN) injury is a major complication of thyroidectomy. This study aimed to investigate the association between preoperative clinical parameters and RLN size prediction. Total thyroidectomy and thyroid lobectomy data were collected between January 2014 and April 2017. Routine identification of the recurrent laryngeal nerves was performed, while intraoperative findings (nerve diameter, thyroid gland weight, intraoperative neuromonitoring (IONM) use, and signal recording) and demographic data were collected for analysis. A total of 848 patients with 1357 RLNs at risk were enrolled in this study. RLN diameter was thinner in females, those with body height <160 cm, and those with a BMI <25 (all p < 0.001). RLN diameter was directly proportional to age, body weight, height, and BMI. RLN diameter was thinner (1.71 mm vs. 1.55 mm, p = 0.039) and branched nerve incidence was higher (18.5% vs. 29.7%, p = 0.09) in the postoperative RLN injury group. Branched nerves were more frequently encountered in female patients (female vs. male: 28.8% vs. 18.7%, p = 0.004). The risk of RLN palsy in intraoperative IONM loss patients was 27 times higher compared to that in IONM normal patients (1.55% vs. 30%, p < 0.001). Thinner nerves did not yield a higher rate of IONM signal loss. Thinner nerves and higher palsy rates could be anticipated in females, younger age groups, those with shorter stature, and those with low BMI. RLN diameter was not associated with the rate of IONM signal loss.

Shaw scalpel use for recurrent laryngeal nerve dissection: safety parameter findings from continuous intraoperative neuromonitoring in swine models

Background

Precise dissection with hemostasis while preserving important structures is critical in thyroid surgeries. In this study, we tested the safety of the Hemostatix Shaw scalpel (HSS) around the recurrent laryngeal nerve (RLN) in porcine models.

Methods

Four piglets were used to obtain continuous intraoperative neuromonitoring data. The HSS was applied at various distances from the RLN, with various temperature settings. Monopolar electrosurgical pencil and Harmonic scalpel were also tested for comparison.

Results

The use of HSS did not show adverse electromyographic (EMG) events when activated at 3- and 5-mm distances from the RLN. At a 1-mm distance, adverse event was observed at 300 °C after 2 seconds of activation. At 210 °C, adverse event was observed when the instrument was directly adjacent to the RLN. For comparison, an electrosurgical pencil, set at coagulation mode (25W), showed an irreversible adverse EMG event during 5 seconds of activation at 1-mm distance from the RLN. Harmonic ACE+, activation power at level 5, was also applied in one RLN and reversable adverse EMG event was observed at <0.1-mm (contact) distance after 3 seconds of activation.

Conclusions

The safety distance of the HSS was 3 mm for the 300 °C setting and >1 mm for the 210 °C setting in the swine models in this study. Surgeons must understand the specific characteristics of various energy devices and apply them appropriately for safe operation.

Investigation of recurrent laryngeal palsy rates for potential associations during thyroidectomy

BACKGROUND

There are many clinical associations and potential mechanisms of injury resulting in recurrent laryngeal nerve palsy (RLNP) after thyroidectomy. One possible cause of RLNP is focal intralaryngeal compression of the recurrent laryngeal nerve (RLN), which may be associated with the tracheal tube (TT). Therefore, we examined current RLNP rates to investigate potential associations, including intralaryngeal, airway, anaesthetic and anthropometric factors.

METHODS

We analysed 1003 patients undergoing thyroid surgery at The Alfred from 2010 to 2017, who had anatomically intact RLNs at the conclusion of thyroidectomy. All included patients underwent pre- and post-operative flexible nasendoscopy. The primary outcome was RLNP rate. We analysed potential associated factors including age, sex, operative time, surgical indication, pathology, American Society of Anaesthesiologists Physical Status, Mallampati scores, body mass index, intubation grade, TT size and specimen weight. The independent risk factors were identified by logistic regression analysis.

RESULTS

Overall, RLNP occurred in 83 patients (8.3%) of which one was permanent (0.1%). On univariate analysis, RLNP was associated with male sex (P = 0.02), and duration of surgery (P = 0.002). On multivariate analysis, both male sex (P = 0.047) and duration of surgery (P = 0.04) remained significant. Further, factors postulated to cause intralaryngeal compression of the RLN, including TT size, body mass index, intubation grade and Mallampati score, were not significantly associated with RLNP.

CONCLUSION

Our study showed a RLNP rate of 8.3%, and associations with longer operative duration, and male sex. Potential intralaryngeal factors were not identified.

Two trajectories of functional recovery in thyroid surgery related unilateral vocal cord paralysis

BACKGROUND

Iatrogenic unilateral vocal fold paralysis caused by thyroid surgery induces profound physical and psychosocial distress in patients. The natural course of functional recovery over time differs substantially across subjects, but the mechanisms underlying this difference remain unclear. In this study, we examined whether the anatomic site of the lesion affected the trajectory of recovery.

METHODS

In this prospective case series study in a single medical center, patients with thyroid surgery-related unilateral vocal fold paralysis were evaluated using quantitative laryngeal electromyography, videolaryngostroboscopy, voice acoustic analysis, the Voice Outcome Survey, and the Short Form-36 quality-of-life questionnaire. Patients with and without superior laryngeal nerve injuries were compared.

RESULTS

Forty-two patients were recruited, among whom 15 and 27 were assigned to the with and without superior laryngeal nerve injury groups, respectively. Compared with the group without superior laryngeal nerve injury, the group with superior laryngeal nerve injury group demonstrated less improvement in the recruitment of vocal fold adductors, and the group also had more severe impairment of vocal fold vibration, maximum phonation time, jitter, shimmer, and harmony-to-noise ratio at the first evaluation. This difference was also found in the glottal gap and maximum phonation time 12 months after the injury.

CONCLUSION

Among patients with thyroid surgery-related unilateral vocal fold paralysis, superior laryngeal nerve injury induces a distinctively different recovery trajectory compared with those without superior laryngeal nerve injury characterized by less reinnervation of vocal fold adductors and worse presentation in terms of the glottal gap and maximum phonation time. This study emphasizes the importance of superior laryngeal nerve function and its preservation in thyroid surgery.

Classification of hyperspectral endocrine tissue images using support vector machines

BACKGROUND

Thyroidectomy is one of the most commonly performed surgical procedures. The region of the neck has a very complex structural organization. It would be beneficial to introduce a tool that can assist the surgeon in tissue discrimination during the procedure. One such solution is the noninvasive and contactless technique, called hyperspectral imaging (HSI).

METHODS

To interpret the HSI data, we implemented a supervised classification method to automatically discriminate the parathyroid, the thyroid, and the recurrent laryngeal nerve from surrounding tissue(muscle, skin) and materials (instruments, gauze). A leave-one-patient-out cross-validation was performed.

RESULTS

The best performance was obtained using support vector machine (SVM) with a classification and visualization in less than 1.4 seconds. A mean patient accuracy of 68% ± 23% was obtained for all tissues and material types.

CONCLUSIONS

The proposed method showed promising results and have to be confirmed on a larger cohort of patient data.

What is the impact of continuous neuromonitoring on the incidence of injury to the recurrent laryngeal nerve during total thyroidectomy?

BACKGROUND

Continuous intraoperative neuromonitoring may facilitate reversal of intraoperative injurious operative maneuvers in comparison with intermittent intraoperative neuromonitoring. The aim of this study was to evaluate the impact of the routine use of continuous intraoperative neuromonitoring on intraoperative injuries to the recurrent laryngeal nerve.

METHOD

This study was a prospective case series with retrospective analysis of consecutive patients undergoing total thyroidectomy from August 2013 to August 2019. During this period, intermittent intraoperative neuromonitoring (before Mar 2016) and continuous intraoperative neuromonitoring (after Mar 2016) were used in all patients.

RESULTS

We reviewed the outcomes of 603 patients (466 female patients) comprising 236 who underwent intermittent intraoperative neuromonitoring and 367 who underwent continuous intraoperative neuromonitoring. Intraoperative adverse electromyography events (>50% decrease in amplitude between VN1 and VN2) were observed in 87 patients (14.5%) and were less frequent in the continuous intraoperative neuromonitoring group (10.6 vs 20.3%, P = .001). Intraoperative loss of signal (electromyography events with VN2 ≤100μV) were observed in 35 patients (5.8%) without any difference between the 2 groups of patients (5.2 vs 6.8%, P = .415). Postoperative recurrent laryngeal nerve palsies were observed in 36 patients (5.9%) without any difference between the 2 groups of patients (4.9 vs 7.6%, P = .168).

CONCLUSION

The routine use of continuous intraoperative neuromonitoring improves the rate of intraoperative adverse electromyography events but does not impact significantly the rates of loss of signal and recurrent laryngeal nerve palsy.

Quantifying the differences in surgical management of patients with definitive and indeterminate thyroid nodule cytology

INTRODUCTION

Thyroid nodules are increasingly common. Despite being an essential pre-operative diagnostic tool, up to 30% of fine needle aspirate cytology (FNAC) yields a non-definitive diagnosis. This study aimed to quantify differences in surgical management of patients with definitive and indeterminate thyroid nodule cytology, and determine if clinical factors can improve cytological diagnosis.

MATERIALS AND METHODS

Patients who underwent thyroidectomy for nodules from 2001 to 2015 were recruited. Those with benign and malignant preoperative cytology were included in the "definitive diagnosis" (DC) group; patients with all other preoperative cytology results were included in the "indeterminate diagnosis" (IC) group. We compared demographics and procedures between these groups. Clinical factors and demographics were also compared between patients with benign and malignant histology in the IC group.

RESULTS

A total of 3821 cases were included. A significantly larger proportion of the IC patients had a hemithyroidectomy (IC 69% vs. DC 39%, p < 0.001) initially, and also had a significantly higher rate of two-stage surgery compared to the DC group (IC 17% vs. DC 11%, p < 0.001). Patients in the DC group were twice as likely to undergo concurrent central lymph node dissection for papillary and medullary cancers than the IC group (p < 0.001). Overall, up to 60% of IC patients had been over- or under-treated at initial surgery. The clinical factors examined were not significantly associated with higher risk of malignancy in IC patients.

CONCLUSION

This study highlights the potential for improved preoperative diagnosis to streamline decision making for surgical management of patients with thyroid nodules.

Effect of surgeons' annual operative volume on the risk of permanent Hypoparathyroidism, recurrent laryngeal nerve palsy and Haematoma following thyroidectomy: analysis of United Kingdom registry of endocrine and thyroid surgery (UKRETS)

PURPOSE

Categorize data to investigate the surgeon volume outcome relationship in thyroidectomies. Determine the evidence base for recommending a minimum number of thyroidectomies performed per year to maintain surgical competency.

METHODS

Data on thyroid operations in the United Kingdom Registry of Endocrine and Thyroid Surgery (UKRETS) from 01/09/2010 to 31/08/2016 was analysed. The primary outcome measure was permanent hypoparathyroidism (PH). Recurrent laryngeal nerve palsy (RLN) and post-operative haematoma were also examined. Exclusion criteria included patient age > 85 or < 18 years, and surgeons contributing <10 operations. Data analysis was performed using general additive models and mixed effect logistic regression for PH and binary logistic regression for others.

RESULTS

For PH 10313 bilateral thyroid operations were analysed. The Annual rate (AR, p = 0.012) and nodal dissection (P < 10^-7) were significant factors. 25,038 thyroidectomies were analysed to investigate the effect of surgeon Volume on RLN palsy and haematoma. Age, retrosternal goitre, routine laryngoscopy, re-operation, nodal Dissection, bilateral thyroidectomy, RLN monitoring and surgeon volume were significantly associated with RLN palsy. Post-operative haematoma showed no significant correlation to surgeon volume. Categorisation of AR showed that PH and RLN palsy rates declined in surgeons performing >50 cases/year to a minimum of 3% and 2.6% respectively in highest volume AR group (>100 cases/year).

CONCLUSION

Surgeon annual operative volume is a factor in determining outcome from thyroid surgery. Results are limited by a high proportion of missing data, which could potentially bias the outcome, but tentatively suggests the minimum recommended number of thyroid operations / year should be 50 cases.

Development of a binational thyroid cancer clinical quality registry: a protocol paper

INTRODUCTION

The occurrence of thyroid cancer is increasing throughout the developed world and since the 1990s has become the fastest increasing malignancy. In 2014, a total of 2693 Australians and 302 New Zealanders were diagnosed with thyroid cancer, with this number projected to rise to 3650 in 2018. The purpose of this protocol is to establish a binational population-based clinical quality registry with the aim of monitoring and improving the quality of care provided to patients diagnosed with thyroid cancer in Australia and New Zealand.

METHODS AND ANALYSIS

The Australian and New Zealand Thyroid Cancer Registry (ANZTCR) aims to capture clinical data for all patients over the age of 16 years with thyroid cancer, confirmed by histopathology report, who have been diagnosed, assessed or treated at a contributing hospital. A multidisciplinary steering committee was formed which, with operational support from Monash University, established the ANZTCR in early 2017. The pilot phase of the registry is currently operating in Victoria, New South Wales, Queensland, Western Australia and South Australia, with over 20 sites expected to come on board across Australia in 2018. A modified Delphi process was undertaken to determine the clinical quality indicators to be reported by the registry, and a minimum data set was developed comprising information regarding thyroid cancer diagnosis, pathology, surgery and 90-day follow-up.

FUTURE PLANS

The establishment of the ANZTCR provides the opportunity for Australia and New Zealand to further understand current practice in the treatment of thyroid cancer and identify variation in outcomes. The engagement of endocrine surgeons in supporting this initiative is crucial. While the pilot registry has a focus on early clinical outcomes, it is anticipated that future collection of longer term outcome data particularly for patients with poor prognostic disease will add significant further value to the registry.

Thyroidectomy Then and Now: A 50-Year Australian Perspective

BACKGROUND

Since the mid-1800s, thyroidectomy has transformed from a procedure associated with high to near-zero mortality. Nonetheless, surgeons must continue to strive to improve patient care. Using historical records and contemporary data, this study compares the practice and outcomes of thyroid surgery at a tertiary institution during two periods, 50 years apart.

METHODS

'The Alfred Hospital Clinical Reports' recorded all cases of surgically managed thyroid disease from 1946 to 1959. These historical cases were compared to contemporary thyroidectomy cases at the Alfred Hospital from 2007 to 2016. Cases were compared for surgical indication and post-operative outcomes.

RESULTS

There were 746 patients in the historical group (mean age 53 years; 87% female) and 787 patients in the contemporary group (mean age 52 years; 80% female). The most common indication for thyroidectomy in both groups was non-toxic nodular goitre. A greater proportion of the contemporary group were diagnosed with thyroid malignancy (27% vs. 8%; p < 0.001). The contemporary group recorded significantly fewer cases of thyrotoxic crisis (2.1% vs. 0%; p = 0.001), permanent nerve palsy (4.6% vs. 0.4%; p < 0.001) and bilateral nerve palsy (1.2% vs. 0%; p = 0.01). There were no mortalities in the contemporary group, while the historical data recorded three deaths (0.44%).

CONCLUSIONS

This study compared thyroid surgery in two cohorts separated by a 50-year period. While it is not surprising that outcomes of thyroidectomy have improved, this study uniquely demonstrates trends of thyroid surgery over time and areas in which further improvements may be made.

Risk factors for thyroid surgery-related unilateral vocal fold paralysis

Objectives/Hypothesis

We aimed to identify the risk factors for iatrogenic unilateral vocal fold paralysis (UVFP) caused by thyroid surgery, to allow the identification of patients requiring nerve‐protection procedures and monitoring technologies.

Study Design

Retrospective case study in a medical center.

Methods

Patients who underwent thyroid surgery from April 2011 to February 2016 and who were diagnosed with UVFP by laryngoscopy and laryngeal electromyography were included. Patient demographics, types of surgery, and characteristics of the thyroid lesions were analyzed.

Results

Sixty (2.1%) of 2,815 patients who received thyroid surgery developed UVFP. The risk of UVFP was higher in patients over 60 years old (odds ratio, 1.89; 95% confidence interval, 1.01‐3.26; P = .01). Involvement of the external branch of superior laryngeal nerve (EBSLN) occurred in 19 (31.7%) of the 60 UVFP patients, and was more likely to occurr in patients with diabetes mellitus (odds ratio, 14.19; 95% confidence interval, 3.80‐52.94; P < .001). The incidence of UVFP and involvement of the EBSLN differed among surgery types, and was the highest among patients undergoing total thyroidectomy with neck dissection (TTND) (10/158, 6.3% and 5/158, 3.2%, respectively).

Conclusions

The risk of thyroid surgery–related UVFP is higher in older patients. EBSLN involvement is more likely in patients with diabetes mellitus. TTND is associated with higher risks of UVFP and EBSLN injury than other types of surgery, implying the need of intraoperative nerve monitoring in these high‐risk characteristics.

Level of Evidence

4 Laryngoscope, 129:275–283, 2019

Compound Motor Action Potential Measures Acute Changes in Laryngeal Innervation

Objective:

Vocal fold paralysis is caused by injury to the recurrent laryngeal nerve (RLN). Current clinical measures of laryngeal innervation are often nonquantitative. Compound motor action potentials (CMAP) measure motor innervation. The goal of this study was to determine whether CMAP can quantify laryngeal innervation following acute nerve injury.

Study Design:

Animal study.

Methods:

Twelve canine hemilaryngeal preparations were used. The RLN was serially stimulated with increasing intensities until the nerve was maximally stimulated. The CMAP amplitude was measured for each intensity stimulation and correlated. Next, the RLN was incompletely transected, and the reduction in CMAP amplitude was correlated to the percentage of transected axons. The percentage of transected axons was determined using horseradish peroxidase (HRP) staining.

Results:

Combining all hemilaryngeal preparations, the submaximal stimulation of the RLN linearly correlated with the resultant CMAP amplitude (r = 0.83; 95% CI, 0.76-0.88). Following partial RLN transection, the percentage of remaining axons linearly correlated with the CMAP amplitude (r = 0.87; 95% CI, 0.34-0.98).

Conclusions:

CMAP amplitude is a quantitative measure that may correlate with the degree of vocal fold innervation in canines. Following RLN injury, CMAP may help clinicians quantify the number of intact axons, assess the likelihood of recovery, and counsel patients on their prognosis.

Risk profile analysis and complications after surgery for autoimmune thyroid disease

BACKGROUND

Surgical approaches to autoimmune thyroid disease are currently hampered by concerns over postoperative complications. Risk profiles and incidences of postoperative complications have not been investigated systematically, and studies with sufficient power to show valid data have not been performed.

METHODS

A prospective multicentre European study was conducted between July 2010 and December 2012. Questionnaires were used to collect data prospectively on patients who had surgery for autoimmune thyroid disease and the findings were compared with those of patients undergoing surgery for multinodular goitre. Logistic regression analysis was used to evaluate risk factors for thyroid surgery-specific complications, transient and permanent recurrent laryngeal nerve (RLN) palsy and hypoparathyroidism.

RESULTS

Data were available for 22 011 patients, of whom 18 955 were eligible for analysis (2488 who had surgery for autoimmune thyroid disease and 16 467 for multinodular goitre). Surgery for multinodular goitre and that for autoimmune thyroid disease did not differ significantly with regard to general complications. With regard to thyroid surgery-specific complications, the rate of temporary and permanent vocal cord palsy ranged from 2·7 to 6·7 per cent (P = 0·623) and from 0·0 to 1·4 per cent (P = 0·600) respectively, whereas the range for temporary and permanent hypoparathyroidism was 12·9 to 20·0 per cent (P < 0·001) and 0·0 to 7·0 per cent (P < 0·001) respectively. In logistic regression analysis of transient and permanent vocal cord palsy, autoimmune thyroid disease was not an independent risk factor. Autoimmune thyroid disease, extent of thyroid resection, number of identified parathyroid glands and no autotransplantation were identified as independent risk factors for both transient and permanent hypoparathyroidism.

CONCLUSION

Surgery for autoimmune thyroid disease is safe in comparison with surgery for multinodular goitre in terms of general complications and RLN palsy. To avoid the increased risk of postoperative hypoparathyroidism, special attention needs to be paid to the parathyroid glands.

Surgical management of the recurrent laryngeal nerve in thyroidectomy: American Head and Neck Society Consensus Statement

"I have noticed in operations of this kind, which I have seen performed by others upon the living, and in a number of excisions, which I have myself performed on the dead body, that most of the difficulty in the separation of the tumor has occurred in the region of these ligaments…. This difficulty, I believe, to be a very frequent source of that accident, which so commonly occurs in removal of goiter, I mean division of the recurrent laryngeal nerve." Sir James Berry (1887).

A meta-analysis of intraoperative neuromonitoring of recurrent laryngeal nerve palsy during thyroid reoperations

BACKGROUND

The rate of recurrent laryngeal nerve (RLN) palsy, a common complication of thyroid surgery, is especially high in thyroid reoperations. The present meta-analysis assesses whether intraoperative neuromonitoring (IONM) reduces the prevalence of RLN palsy in thyroid reoperations.

DESIGN AND METHODS

A systematic literature search was conducted in the PubMed, SCIE and Wan Fang databases for studies published up to 31 August 2016. All data were analysed using STATA (version 11) software. Publication bias was assessed using Begg's funnel plot and Egger's test, and sensitivity analysis was performed.

RESULTS

Nine studies including 2436 at-risk nerves met the inclusion criteria. The results were presented as pooled relative risks (RRs) with 95% confidence intervals (CI). The overall RLN palsy rate was significantly lower in reoperations conducted with IONM than in those conducted without IONM (RR=0.434, 95% CI=0.206-0.916, P=.029). High heterogeneity was found (I² =70.2%, P=.001). The rates of transient RLN palsy with and without IONM did not differ significantly (RR=0.607, 95% CI=0.270-1.366, P=.227). The heterogeneity was high (I² =67.4%, P=.005). However, IONM was significantly associated with a reduction in permanent RLN palsy (RR=0.426, 95% CI=0.196-0.925, P=.031). No significant heterogeneity was found (I² =13.7%, P=.325). Funnel plots for overall and transient RLN palsy showed a possible publication bias.

CONCLUSIONS

Intraoperative neuromonitoring (IONM) is associated with a reduction in overall and permanent RLN palsy in thyroid reoperations. However, given the limited sample size and heterogeneity in this meta-analysis, further studies are required to confirm our preliminary findings.

Extralaryngeal division of the recurrent laryngeal nerve: A common and asymmetric anatomical variant

OBJECTIVE

Recognition of extralaryngeal branching of the recurrent laryngeal nerve is crucial because prevention of vocal cord paralysis requires preservation of all branches of the recurrent laryngeal nerve. We assessed the prevalence of extralaryngeal branching of the recurrent laryngeal nerve and the median branching distance from the point of bifurcation to the entry point of the nerve into the larynx.

MATERIAL AND METHODS

Prospective operative data on recurrent laryngeal nerve branching were collected from 94 patients who underwent thyroid or parathyroid surgery between September 2011 and May 2012.

RESULTS

A total of 161 recurrent laryngeal nerves were examined (82 right, 79 left). Overall, 77 (47.8%) of 161 recurrent laryngeal nerves were bifurcated before entering the larynx. There were 36 (43.9%) branching nerves on the right and 41 (51.9%) branching nerves on the left, and there was no significant difference between the sides in terms of branching (p=0.471). Among 67 patients who underwent bilateral exploration, 28.4% were found to have bilateral branching, 40.3% had unilateral branching, and the remaining 31.3% had no branching. The median branching distance was 15 mm (5-60mm).

CONCLUSION

Extralaryngeal division of recurrent laryngeal nerve is a common and asymmetric anatomical variant. These variations can be easily recognized if the recurrent laryngeal nerve is identified at the level of the inferior thyroid artery and then dissected totally to the entry point of the larynx. Inadvertent division of a branch may lead to vocal cord palsy postoperatively, even when the surgeon believes the integrity of the nerve has been preserved.

Experience with intraoperative neuromonitoring of the recurrent laryngeal nerve improves surgical skills and outcomes of non-monitored thyroidectomy

PURPOSE

Intraoperative neuromonitoring (IONM) can serve as a tool to increase skills in recurrent laryngeal nerve (RLN) identification and complete removal of thyroid tissue. The aim of this study was to validate this hypothesis.

METHODS

This prospective study involved 632 patients (1161 RLNs at risk) who underwent thyroid surgery in 2011-2014. Although IONM was not used until 2012, this prospective study started on 1 January 2011. The three participating surgeons knew about the study before that date and that the rate of RLN identification would be carefully measured in total and near-total surgery. Solely, visual identification of the RLN was used throughout 2011. IONM was introduced as a training tool in 2012-2014 for the first 3 months of each year. In the remaining months, thyroid operations were performed without IONM. Outcomes of non-monitored thyroid operations were compared before (01-12/2011) vs. after (04-12/2012-2014) 3 months of exposure to IONM yearly (01-03/2012-2014). The rate of RLN identification was assessed in total and near-total thyroidectomies and in totally resected lobes in Dunhill's operation. The prevalence of RLN injury and the utilization of total thyroidectomy were evaluated.

RESULTS

In 2011, the rate of successful RLN visual identification in total and near-total thyroidectomies and in totally resected lobes in Dunhill's operation was 45.71 %. After the introduction of IONM in 2012-2014, in the procedures performed without IONM, the rate was 86.66, 90.81, and 91.3 %. The prevalence of RLN injury in 2011 was 6.8 %, while in the years following the introduction of IONM, it was 3.61, 2.65, and 1.45 %. Utilization of total thyroidectomy increased from 47.9 % in 2011 to 100 % in 2014.

CONCLUSIONS

Experience with IONM led to an increase in RLN identification (p < 0.0001), a decrease of RLN injury (p < 0.05), and an increase in the safe utilization of total thyroidectomy (p < 0.0001) in non-monitored thyroid operations. IONM is a valuable tool for surgical training.

Early discharge after total thyroidectomy: a retrospective feasibility study

AIM

The continued hospitalization after total thyroidectomy is often due to the onset of hypocalcemic complications more than 24 hours after surgery. So it would be important to predict which patients will not develop the hypocalcemic complication to discharge them early. This was the aim of our study.

PATIENTS AND METHODS

Our retrospective study was conducted on 327 consecutive thyroidectomized patients, operated on for benign and malignant diseases. We evaluated the values of preoperative serum calcium levels (Cal0) and of the first postoperative day (Cal1) and two new variables were calculated (dCal and dCaln). The same thing was made on a subgroup of 111 patients in whom also parathiroyd hormone (PTH) values were detected. Statistical analysis was performed with the goal of determining if we could establish a safe criterion for discharge at 24 hours after surgery and if there is a correlation between suitability for discharge and diagnosis.

RESULTS

As to discharge, the predictive power of the discriminant function applied was significant both on the total of patients and in the subgroup of 111 patients, but it was clinically unacceptable because it would expose us to a 21% to 27% error rate. It is not possible to identify a threshold, below which to consider patients surely dischargeable. The diagnosis does not appear correlated with the suitability for discharge.

CONCLUSION

On the basis of serum calcium and PTH levels in the first postoperative day, it is impossible to predict which patients can be discharged 24 hours after surgery without incurring in hypocalcemic complications.

The influence of American Society of Anesthesiologists Physical Status on patient morbidity and survival after total thyroidectomy

In cases of thyroid papillary carcinoma, a less aggressive cancer, surgeons may hesitate to perform total thyroidectomy on patients with poor general condition because these may experience longer survival without undergoing surgery. To investigate the influence of general patient condition on the patients' survival who received total thyroidectomy, we utilized the American Society of Anesthesiologists Physical Status (ASA-PS). We retrospectively reviewed all patients undergoing total thyroidectomy under general anesthesia and graded by ASA-PS between 2004 and 2014. Patients with anaplastic carcinoma and metastatic thyroid renal cell carcinoma were excluded. There were 77 (30%), 149 (58%), and 30 (12%) ASA-PS 1, 2, and 3 cases, respectively. Patient age increased significantly with increasing ASA-PS score (median age of 53, 64, and 71 years for ASA-PS 1, 2, and 3). Hospitalization periods extended significantly for patients with ASA-PS 3. Twenty patients died during the study (3.89 median years). Five-year overall survival rates were 100%, 93%, and 79% for ASA-PS 1, 2 and 3, respectively. Patients in the ASA-PS 1 group had significantly better prognosis by log-rank test. Univariate analysis showed an increased risk of death as ASA-PS score increased (hazard ratio: 3.03, 95% confidence interval: 1.55-5.92, p=0.00). In multivariate analysis, including patient age and presence of malignancy, patient age was the only significant predictor of overall survival (hazard ratio: 1.09 by year, 95% confidence interval: 1.03-1.14, p=0.00). We concluded that a high ASA-PS score should not inhibit performance of total thyroidectomy if a patient's age is suitable for the surgery.

Intermittent neural monitoring of the recurrent laryngeal nerve in surgery for recurrent goiter

Reoperative thyroid surgery is still challenging even for skilled surgeons, and is associated with a higher incidence of complications, such as hypoparathyroidism and recurrent laryngeal nerve (RLN) palsy. Displacement of the RLN, scar tissue from previous neck surgery and difficulty in maintaining good hemostasis are risk factors in reoperations. The prevalence of RLN injury in reoperative thyroid surgery ranges as high as 12.5% for transient injury and up to 3.8% for permanent injury. Bilateral paresis can also occur during reoperations, and is a dangerous complication influencing the quality of life, sometimes requiring tracheostomy. RLN identification is the gold standard during thyroidectomy, and the use of intraoperative neuromonitoring (IONM) can be a valuable adjunct to visual identification. This technique can be used to identify the RLN and the external branch of the superior laryngeal nerve (EBSLN), both of which are standardized procedures. The aim of this review was to evaluate the use of intermittent neural monitoring of the RLN in surgery for recurrent goiter, and to assess the prevalence of RLN injury while using IONM reported in the current literature.

A retrospective evaluation of the etiology of unilateral vocal fold paralysis over the last 25 years

Previous studies have shown that the etiology of laryngeal paralysis has changed over the last decades, with an increase in the incidence of cases attributable to thyroid surgery. The aim of this study was to evaluate longitudinal changes in the etiology of unilateral vocal fold paralysis (UVFP) in a single institution over the last 25 years. This retrospective study analyzed the etiology of UVFP between 1990 and 2015 by comparing a cohort of patients treated in 1990-1992 with a cohort treated in 2013-2015. The final analysis was based on data concerning 356 patients (38.8 % males; mean age 55.3 ± 20.4 years): 113 in the 1990-1992 cohort, and 243 in the 2013-2015 cohort. The main cause of UVFP in the population as a whole was thyroidectomy (41.3 %), followed by an idiopathic origin (25.3 %) and thoracic surgery (12.1 %); this was confirmed in both intra-group analyses. There was a statistically significant association between etiology and the sub-group periods: the prevalence of post-thyroidectomy UVFP was highly significantly lower in the 2013-2015 cohort (35.4 vs 54.0 %), and the prevalence of idiopathic cases was higher (28.4 vs 18.6 %). Etiology significantly related to gender in both cohorts (p value ≤0.001). In the 2013-2015 cohort, there was also a statistically significant relationship between etiology and age classes (p value 0.017), and the left side was more frequently affected than the right (67.1 vs 32.9 %). Our findings document changes in the etiological pattern of UVFP over the last 25 years, with a considerable decrease in post-thyroidectomy UVFP, and a growing predominance of idiopathic and post-thoracic surgery UVFP.

Distinct Disease and Functional Characteristics of Thyroid Surgery-Related Vocal Fold Palsy

BACKGROUND

Iatrogenic trauma induced by thyroid surgery is the most common etiology of unilateral vocal fold paralysis (UVFP). UVFP after thyroid surgery may lead to profound physical and psychosocial distress. This study comprehensively evaluated UVFP caused by thyroid surgery, and compared the results with those caused by other surgical trauma.

METHODS

Patients with surgery-related UVFP were evaluated using quantitative laryngeal electromyography, videolaryngostroboscopy, voice acoustic analysis, the Voice Outcome Survey, and the Short Form-36 Health Survey quality-of-life questionnaire. Patients with thyroid surgery and other surgeries were compared.

RESULTS

A total of 105 patients were recruited, of whom 52 and 53 were assigned to the thyroid surgery and the other surgery group, respectively. Patients in the thyroid surgery group had a higher proportion of external branch of superior laryngeal nerve (eSLN) involvement, longer duration from disease onset to the first laryngeal electromyography examination, lower jitter, higher harmonic-to-noise ratio, and better quality of life compared with the other surgery group. Specifically for patients in the thyroid surgery group, those with eSLN involvement tended to have more pronounced impairment in jitter and shimmer compared with patients without eSLN involvement.

CONCLUSION

UVFP caused by thyroid surgery has a distinct clinical presentation with relatively high involvement in the eSLN, better voice acoustics, longer waiting time before asking for evaluation, and less impact on quality of life. The involvement of eSLN in these patients further impaired their voice. Early referral is suggested for these patients, especially with suspected eSLN injury.

The weepy nerve-different sensitivity of left and right recurrent laryngeal nerves under tensile stress in a porcine model

PURPOSE

Recurrent laryngeal nerve palsy in thyroid surgery is still a threatening complication. Our aim was to analyze the impact of prolonged tensile stress on the recurrent laryngeal nerve (RLN) in an animal model using continuous intraoperative neuromonitoring (C-IONM).

METHODS

Constant tensile stress was applied to left and right RLNs in 20 pigs (40 RLN). In a pilot study, five animals were subjected to a tensile force of 0.34 ± 0.07 N for 10 min and changes in amplitude were documented using C-IONM. In the main study, a force of 1.2 N was applied until the signal amplitude was reduced by 85 %, in 15 pigs. Nerve conductivity was analyzed by threshold current measurements.

RESULTS

Good correlation was found between stress and amplitude decrease in the pilot study as well as between signal decrease and duration of trauma in the main study. Great variations were found inter- and intra-individually. These variations were most prominent at 85 % signal reduction (median 36 min, range 0.3-171 min). There was no side specificity (left 0.3-171 min, right 0.3-168 min, respectively, p = 0.19). However, in each individual animal, there was a sensitive (0.3-98.9 min) and less sensitive nerve (26.8-171 min). These differences became highly significant at 85 % of signal reduction (p = 0.008), where the vulnerability is 1.4 to 146.4 times higher on one side (mean 4.3).

CONCLUSIONS

Our study demonstrates the presence of a sensitive RLN that was 4.3 times more vulnerable than the contralateral nerve (range 1.4-146.4 times, p = 0.008). Thus, the right and the left nerves cannot be assumed to be of equal sensitivity to trauma. In our data, the more sensitive nerve does not occur predominantly on one side and was named the "weepy nerve."

A Closer Look at the Recurrent Laryngeal Nerve Focusing on Branches & Diameters: A Prospective Cohort Study

AIM

We aimed to investigate the anatomical characteristics of the recurrent laryngeal nerve (RLN) highlighting on its diameter and branching pattern.

MATERIALS AND METHODS

We prospectively collected 215 patients (178 female, 37 male) who underwent thyroid/parathyroid surgery during over a 2-year period. Apart from demographic features and surgical data, diameter of RLNs, and their branches and as well as branching distance (distance between the point of bifurcation and the laryngeal entry of RLN) were recorded.

RESULTS

In 215 patients, 378 RLNs were assessed and 42% (n = 159) bifurcated RLNs were observed. The bifurcation rate was similar on the right and left side(s) of the neck (40% and 44%, respectively; p = 0.47). In those, who underwent bilateral exploration, in the case of bifurcation on the first side of the neck, the possibility of contralateral bifurcation was approximately 50%, whereas this rate was found to be only 30% in those with nonbranching RLNs. Mean branching distance was 18 ± 9 mm, and it was similar on the right and left sides (17 and 19 mm, respectively). Approximately 80% of bifurcations were observed within 5-24 mm of the RLN. Mean diameter of the anterior branches was found to be significantly larger compared to posterior branches (1.09 ± 0.35 and 0.82 ± 0.36 mm, respectively; p < 0.01).

CONCLUSIONS

There is great variability in RLN branching. We observed that approximately two out of three bifurcations were unilateral and anterior branches were thicker compared to posterior branches. These findings should be taken into consideration to avoid any damage to the RLN during thyroid and parathyroid surgery.

Predictors of metastasis to lymph nodes posterior to the right recurrent laryngeal nerve in differentiated thyroid carcinoma: A prospective study

OBJECTIVES

To study the clinicopathological characteristics and the risk factors of lymph nodes posterior to the right recurrent laryngeal nerve (LN-prRLN) metastasis in differentiated thyroid carcinoma; and to identify the indication for LN-prRLN dissection.

METHODS

We treated 145 patients with differentiated thyroid carcinoma with appropriate surgical intervention. The specimens were examined by the pathologists. The right paratracheal lymph nodes were divided into two groups: anterior or posterior to right recurrent laryngeal nerve (VIa or VIp compartment, respectively). We recorded the clinical characteristics, histopathological features of the primary tumors, and lymph node metastasis of the patients. The results were statistically analyzed.

RESULTS

There were 85 patients (58.6%) with central lymph node metastasis, of whom 61 (42.1%) had metastasis in VIa compartment; 16 patients (11.0%) had VIp subdistrict metastasis; and 25 patients had lateral lymph node metastasis. Multiplicity, larger tumor (≥1 cm), and coexistence of central lymph node metastasis, VIa compartment metastasis, and lateral lymph node metastasis were all significantly related with LN-prRLN metastasis, while sex, age, location of the tumor, and extrathyroid extension of the tumor showed no significant relation (p > 0.05).

CONCLUSION

The incidence of LN-prRLN metastasis was lower than other central lymph nodes, as well as lymph nodes anterior to right recurrent laryngeal nerve. When there were multiple foci of tumors, or the tumor was larger than 1 cm, or central or lateral LN metastasis was indicated by preoperative ultrasound or confirmed by intraoperative frozen sections, it is strongly recommended that exploration and dissection of the LN-prRLN should only be performed by experienced surgeons.

Recurrent laryngeal nerve safety parameters of the Harmonic Focus during thyroid surgery: Porcine model using continuous monitoring

OBJECTIVES/HYPOTHESIS

The Harmonic Focus (HF) is one of the most popular energy-based devices. The aim of this study was to provide recurrent laryngeal nerve (RLN) functional data that define the safety parameters of the HF during thyroidectomy.

STUDY DESIGN

Prospective porcine model using continuous electrophysiologic monitoring.

METHODS

Ten piglets were used. At varying distances from the RLN, the HF was activated (activation study). The HF was also applied directly on the RLN after activation on sternocleidomastoid muscle for 10 seconds with different cooling times (cooling study).

RESULTS

In the activation study, there was no adverse electromyography (EMG) event at more than 1 mm distance. In the cooling study, there was no adverse EMG event after a 10-second cooling period. When the HF was cooled on the sternocleidomastoid muscle, there was no adverse EMG event after 2 seconds cooling time.

CONCLUSIONS

The safe distance of the HF was 1 mm, and it should be cooled for more than 10 seconds or 2 seconds after cooling on muscle. The HF should be used in a standardized manner to avoid RLN injury.

LEVEL OF EVIDENCE

NA.